Air mattress



FIG. 1 is a perspective view of an air mattress showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a left side elevation view thereof;

FIG. 5 is a right side elevation view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines depict portions of the air mattress that form no part of the claimed design. 

CLAIM The ornamental design for an air mattress, as shown and described. 